Method of and means for secret signaling



Aug. 7, 1923. 1,464,086

w. E. BEATTY METHOD OF AND MEANS FOR SECRET SIGNALING Filed Dem/27, 1918E Printing M///amf 564/0.

Patented Aug. 7,1923. I

UNITED STATES PATENT OFFICE.

WILLIAM E. BEATTY, OF BAYSIDE, LONG ISLAND, NEW YORK, ASSIGNOR TOWESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., ACORPORATION OF NEW YORK.

Application filed December 27, 1918. Serial No. 268,467.

I T 0 all whom it may concern:

means for secret signaling and more par-- ticularly to secret signalingsystems in which carrier waves are modulated in accordance with signals.

An object of the invention is to provide means for transmittingsignaling or control impulses which cannot be intercepted byunauthorized parties.

A further object of the invention is to provide a transmission systemwhich may transmit simultaneously successive portions of a message orseries of control impulses.

Anotherfeature of the invention is the provision of keyboard operatedapparatus by means of which successive portions of the message may bestored up and then simultaneously transmitted.

In the ordinary method of signaling successive elements of the signal ormessage as, for example, the successive characters or letters used, aretransmitted in their proper successiv order. According to this inventiona plurality of such successive elements are transmitted simultaneouslyand these elements, simultaneously received at a receiving station, aredistinguished from each other and arranged in their proper sequence toproduce an intelligible signal or message. In order to mak it possibleto distinguish th simultaneously transmitted characters it is necessaryto transmit each as an energy variation having a characteristicdistinctive from that of the others. A system in which each characteris'transmitted as a modulation of an individual carrier wave wouldsatisfy this requirement. A more satisfactory system, at least from thestandpoint of secrecy, is one in which all the simultaneouslytransmitted characters are transmitted as modulations of the samecarrier wave, the modulation for each character, however, beingdifferent from that for any of the other simultaneously transmittedcharacters, as is the case in the successive modulation system whichwill later be described.

Further objects and advantages of the invention will appear from thefollowing detailed description taken in connection with the accompanyingdrawings, in which Fig. 1 is a diagrammatic view of a radio transmittingstation with means for permitting simultaneous transmission of twosuccessive portions of a telegraphic message or series of controlimpulses; Fig. 2 is a similar view of an arrangement of printingtelegraphs and auxiliary keyboard mechanism, whereby a single operatormay cause simultaneous transmission of successive elements of a signal;Fig. 3 is a detail view of a single key; and Fig. 4: is a diagrammaticview of a radio receiving system adapted to operate in conjunction withthe transmitter of Fig. 1.

Referring to Fig. 1, a high frequency generator l is connected bytransformer 2 to the input circuit of a thermionic modulator 3.

source 9, are connected to the input circuit of a thermionic modulator11. The output circuits of modulators 8 and 11 are each connected to theinput circuit of modulator 3, the output circuit of which is connectedthrough a thermionic amplifier'lQ to an antenna or transmissionconductor 13.

The operation of this system is as follows: An operator is assigned toeach of keys 6 and 7, respectively, which may be taken as representativeof any transmitting device, such as a simple key or interrupter, or animpulse combination transmitter of a printing telegraph. Sources 9 and10 produce intermediate carrier frequency oscillations for example, of20,000 and 30,000 cycles per second, respectively. Low frequencyimpulses from source 4: are impressed toget er with the intermediatecarrier frequency oscillations from source 9 on modulator 8, the outputcircuit of which supplies modulated oscillations of the intermediatecarrier frequency to the input circuit of modulator 3, to whichoscillations of the high carrier frequency are supplied by source 1. Ifthe source 1 produces 100,000 oscillations per second. oscillations ofthat frequency modulated in accordance with modulated intermediatecarrier oscillations from modulators 8 and 11 will be transmitted fromthe output circuit with an intermediate carrier frequency,

which in turn is modulated by variation currents from source 4.

Suppose, for example, that the word Eastern is to be transmitted. Theword may be divided into the two groups of letters E, S, E, N and ATR.The operator at key 6 operates that key to transmit the first group andthe operator at key 7 0 crates key 7 to transmit the second group.-onsequently the transmission of characters of one group partly or whollyoverlaps the'transmission of the other group. The energy radiated fromantenna 13 is in the form of successively modulated high-frequencycarrier waves of one intermediate carrier frequency carrying the impulsevariations corresponding to letters E, S, E, N, and high frequencycarrier waves modulated by another intermediate carrier frequencycarrying the impulse variations corresponding to the letters ATR.

Fig. 2 illustrates a transmitting system usingthree printing telegraphtransmitters 14,15 and 16, each under the control of an auxiliarykeyboard apparatus 17, 18, '19.

Each printing telegraph transmitter is of the ordinary type in whichletters and other characters are transmitted as combinations of,electrical impulses. Auxiliary keyboard 17 with a contact member 21 andhas a project ing locking or detent lug 31. A cooperating sliding latch32 is normally held in contact with key 20 by a resilient member 33acting to force the latch away from fixed frame member 34. A spring 35or equivalent device holds key 20 in raised position. The depression ofkey 20 permits latch 32 to engage lug 31 and lock the key in depressedposition until released by a slow-acting solenoid coil 36, which uponenergization retracts latch 32 against the action of member 33 andpermits spring 35 to return key 20 to normal or raised position out ofcontact with contact member 21. Keys 20 are each connected to a commonlead 22 connected to the movable contact of a master key 30, the lowerfixed contact 29 of which is connected to a source 23 of electriccurrent. The contact members 21 are insulated from each other and fromtheframe work of the keyboard. A removable operating board 24 isdetachably connected to transmitter 14 and has an electromagnetictapping device 25 arranged over each key 26 of transmitter 14 inposition to strike its corresponding key when energized. Each contactmember 21 is connected to a conductor 27 which includes the winding of acorresponding tapping device or tapper 25 and terminates in a commonconductor 28 connected to the pole of source 23 which is electricallyremote from contact 29 of master key 30. Each solenoid 36 has oneterminal connected to conductor 22 and the other terminal connected toconductor 28. The circuits of auxiliary keyboards 18 and 19 and theircorresponding transmitters l5 and 16 are in every respect like thosejust described.

Suppose that the syllable cab is to be transmitted, the operatordepresses key C on auxiliary keyboard 17, and keys A' and B on keyboards18 and 19 respectively. Each depressed key looks down. For each of thedepressed keys an energizing circuit is now prepared as follows: lowercontact 29 of key 30, source 23, conduct-or 28, tapper winding 25,contact 21, de-

pressed key 20, conductor 22 to key30. Each solenoid coil 36 is also ina circuit with source 23 which is open only at master key 30.Consequently, the closure of key 30 actuates tappers 25 simultaneouslyto set up corresponding telegraphic combinations and also actuatesslow-acting solenoids 36 to withdraw all'the latches 32 and release alldepressed keys shortly after the combi nations are set up. Since eachtransmitter 14, 15, 16 is assigned one of three successive portions ofthe message, these three portions are transmitted simultaneously. Thethree transmitters 14, 15, 16 are each arranged in a transmission systemsuch as described in connection with Fig. 1, each printing telegraphbeing substituted for one of the low frequency signaling sources and itskey. It will of course be understood that although two signaltransmitters are indicated in Fig. 1 and three in Fig. 2,any number maybe used, the circuit arrangements for additional ones corresponding inevery way to those shown, with an individual intermediate carrierfrequency source for each.

Fig. 4 illustrates a receiving system comprising an antenna or receivingconductor 37 and a thermionic detector 38 connected thereto, having anoutputv circuit inductively connected to circuit 39 ,in which a numberof tuned selecting circuits 40 are arranged in series. Each selectingcircuit is tuned for a particular intermediate carrier frequency andserves as an input circuit for a thermionic detector 41 individualthereto, the detector having an output circuit arranged to supplydetected impulses or variation currents to a receiving printingtelegraph deand ratchet mechanism, the operation of 'ters 'upon anindividual any one of the receivers 42 will serve to move the tape.

Assume that the transmitting apparatus illustrated in F ig. 1 is beingused to transmit the word Eastern to the receiving apparatus of Fig. 4.Successively modulated waves carrying simultaneouslg the characterimpulses of letter E and are received by antenna 37. successivelymodulated oscillations are accordingly supplied to detector 38 andsingly modulated current components of the two intermediate-carrierfrequencies appear simultaneously in its output circuit. Correspondinglymodulated currents of these two frequencies are supplied to circuit 39.One tuned input circuit 40 selects the modulated intermediate carrierfrequency oscillations of the frequency produced in the output circuitof modulator,

8, and the other circuit 40 is tuned to select the currents of thefrequency set up in the output circuit of modulator 11. Detectors 41will accordingly supply to their respectiveprinters 42, impulsescorresponding to those supplied by the circuits of sources 4 and 5, andthe printers print letters E and A respectively on the traveling tape,one printer printing its character on a portion of the tape slightly inadvance of the portion upon which the other printer operates. The tapeis fed forward after each printing operation adistance sufficient tovaccommodate as many successive characters as there are printers.Obviously each print ing telegraph may operate to print charactape. Thetapes may then be assembled side by side to read the message.

The printing telegraph receivers 42 might equally well be replaced byMorse recorders in the case of Morse signal transmission, or if controlimpulses are being sent out to select or control circuits, each receivermay control a selector of any suitable sequence selecting mechanism, thejoint action of the selectors serving to select the desired element orcircuit.

The thermionic modulators, detectors and amplifiers have all beenillustrated as of the ordinary highly evacuated thermionic typeincluding a heated cathode, an anode and an impedance controllingelement. Each may, however, be replaced by equivalent functioningapparatus of any desired form. It should also be understood that dynamoelectric alternators or vacuum tube oscillators or any other type ofalternating current sources of the proper frequency may be used. As inthe ordinary case, high frequency wire transmission may be employedinstead of radio transmission.

This system is secret to theextent that successively modulated wavesrequire for their detection either a local source of high frequencyoscillations of proper frequency, or a tandem arrangement of detectorsand further that anyone attempting to pick up the message would succeedin getting only the portion carried on one intermediate carrierfrequency. Since the number of intermediate carrier frequencies may bemade large,

the task of intercepting the entire message mag be made very difficult.

lthough the invention has been illustrated and described in connectionwith certain specific forms of radio transmission circuits, it is to beunderstood that it is not limited to any of the specific systems orfeatures involved in these systems, but only by the scope of theappended claims.

What is claimed is:

1. The method of signal transmission which comprises producing aplurality of different waves modifying each in accordance with anindividual one of a series of sequentially occurring elements of asignal and simultaneously modifying a common carrier Wave by all of saidplurality of modified waves.

2. The method of signal transmission which comprises transmittingsequentially groups of elements of a signal, each group comprising aplurality of successive elements of the signal, the transmission of allof the elements of any 'one group being concurrent.

3. The method which comprises producing energy representing a pluralityof successive elements of the same signal and modulating a commoncarrier wave simultaneously in accordance with the energy representingall of said plurality of elements.

4. The method of impulse transmission which comprises transmitting acarrier wave havin a plurality of different successive modu ationsrepresenting successive elements of a series of impulses.

5. The method of impulse transmission which comprises transmitting acarrier wave having a plurality of. different successive modulations,receiving said carrier wave and producing an intelligible recordthereby.

6. The method of signal transmission comprising successively setting updifferent elements of a signal and simultaneously transmitting saiddifferent elements.

7. The method of storage transmission which comprises storingsuccessively a plurality of elements of a message and then transmittingenergy simultaneously representing all of said elements.

8. The method of impulse transmission v '10. A transmission systemcomprising means for simultaneously transmitting on different frequencycarrier waves, a plurality of'predetermined portions of a series ofimpulses.

11. A transmission system comprising means for successively storing upelements of a message, and means for simultaneously transmitting energyrepresenting said elements.

12. A signal transmission system comprising a signal transmitter,meansfor succes sively setting 11 in said transmitter different elements0 the signal and means for simultaneously transmitting said difierentelements over a transmission circuit.

13. A transmitting arrangement comprising a plurality of charactermembers, means for operating said members in succession, and means forcausing said plurality of character-members, after each has been op-'erated, to simultaneously transmit impulses corresponding to theirrespective characters.

14. A transmitting device, an impulse transmitter having a plurality ofcharacter elements, means for operating said elements in a timesuccession, a transmitting circuit under the control of each of saidcharacter elements, and means to cause a plurality of said characterelements, after all have been operated, to act simultaneously upon said.

transmitting circuit.

l5.- A storage transmlssion system, comprising means for successivelystoring up a plurality of elements of a message and means fortransmitting energy simultaneously representing all of said elements.

16. In combination, a printing telegraph transmitter having a pluralityof keys, means associated with each' of. said keys to transmit energyhaving characteristics individual to that key, a controlling devicehaving a number of keys each of which corresponds to a. key of saidtransmitter, and

means whereby successive operation of the keys of said controllingdevice causes simultaneous operation of the corresponding keys of saidtransmitter.

In witness whereof, I hereunto subscribe my name this 20th day ofDecember, A. D.,

WILLIAM E. BEATTY.

